1. Field of the Invention
This invention relates generally to the field communications, and more specifically to the field of secure communications.
2. Description of the Prior Art
There are many applications where it is desirable for one party to communicate with a second party in a manner such that access to the communication is prohibited to all unauthorized parties. It is desirable that this access be prohibited either through accident or by intent, whether overt or covert, and regardless of the degree of sophistication of the unauthorized parties seeking access. In the past, a number of techniques have been utilized to this end. For example, encryption systems have been utilized wherein the message is unintellible to a party lacking the necessary key, even though access to the communication itself is not prohibited. A second technique commonly employed is to route the communication over a line, access to which is prohibited by some physical means. Typical of this second kind of system, and the one which is considered by the applicant to be most nearly relevant in the prior art to the subject invention, is described in U.S. Pat. No. 3,700,900 to Herleikson. A secure optical fiber transmission system is disclosed therein, which includes the optical fiber encased in a hollow, tubular high voltage transmission line conductor. The high voltage precludes unauthorized access to the data carried by the light beam inclosed therein. The disadvantage of such a system lies in the fact that means for penetrating the high voltage shield are available despite the danger therein, by utilizing techniques known to power distribution utility companies. In such a case, unauthorized access to the communication would be allowed without the knowledge of the communicators. It is desirable to have a secure communications system which insures communication between the intended parties, which prohibits access to the communication to unauthorized parties, and which insures that attempts at penetrating the secure system would be recognized by the intended parties. It is to this end that the present invention is directed.